As the memory capable of storing mass data for use, a variable resistance memory (ReRAM) and so forth, which can be easily formed in three dimensions, has received attention. Even though any types of cells are used, however, fragmentation of the cell state in several levels to put plural bits in a single cell is effective on achievement of mass storage. With this regard, examples can be found in a NADN-type flash memory.
If such the multi-level cells are used, however, the instability of setting the cell state makes failed write easily occur. Thus, it has a tradeoff with the increase in the number of levels. Therefore, the NADN-type flash memory cannot provide more than 8 or 16 levels and causes a complicated association between data and levels additionally.